Calculate excess weight from current weight and height, or estimate % excess weight loss from starting weight, current weight and reference BMI.

Compare current weight with the selected BMI reference.

For adults. BMI 25 is a comparison reference, not an individual ideal weight or treatment goal. BMI does not measure body fat or diagnose health.

Excess Weight Formula

The calculator uses a different formula for each mode.

Weight difference from BMI reference:

Excess weight = Current weight − (Target BMI × Height²)

Percent excess weight loss (%EWL mode):

%EWL = (Starting weight − Current weight) / (Starting weight − Reference weight) × 100

Weight difference from a known reference:

Excess weight = Actual weight − Reference weight
  • Current / Actual weight — what you weigh now.
  • Starting weight — your weight at the start of tracking, often the pre-op weight in bariatric care.
  • Reference weight — the reference weight, either entered directly or computed from a target BMI.
  • Target BMI — the BMI value used to define reference weight (BMI 25 is the threshold for the adult overweight screening category, not an individual ideal).
  • Height — measured in meters when applied in the BMI formula.

Heights and weights are converted to metric internally (kg and m). BMI-based reference weight is a screening estimate for adults; it does not adjust for muscle mass, frame size, age, or pregnancy. For pediatric or clinical decisions, use a method appropriate to the patient.

Reference Tables

Use these to interpret the numbers the calculator returns.

BMI Adult category
Below 18.5Underweight
18.5 to less than 25Healthy range
25 to less than 30Overweight
30 to less than 35Obesity class I
35 to less than 40Obesity class II
40.0 and aboveObesity class III

Illustrative %EWL intervals. These are not universal clinical success or failure criteria; interpretation depends on the procedure, follow-up and patient context.

%EWL Typical interpretation
Below 25%Below 25% of starting excess lost
25% to less than 50%25% to less than 50% of starting excess lost
50% to less than 75%50% to less than 75% of starting excess lost
75% and above75% or more of starting excess lost

Worked Example

A person is 5 ft 8 in (1.7272 m) and weighs 230 lb (104.3 kg). Using a BMI 25 target:

  • Reference weight = 25 × 1.7272² ≈ 74.5795 kg (about 164.4205 lb)
  • Excess weight = 104.3262 − 74.5795 ≈ 29.7467 kg (about 65.5795 lb)

After surgery they drop to 180 lb (81.6 kg). %EWL:

  • Weight lost = 230 − 180 = 50 lb
  • Starting excess = 230 − 164.4205 ≈ 65.5795 lb
  • %EWL = 50 / 65.5795 × 100 ≈ 76.2%

FAQ

Which target BMI should you use? BMI 25 is the threshold for the adult overweight screening category and a convention used in some excess-weight-loss calculations. The reference is not an individual treatment goal; use the convention agreed with your clinician.

Why does my %EWL change if I switch the target BMI? %EWL depends on reference weight, and reference weight depends on the target BMI you choose. A lower target BMI raises starting excess, which lowers the %EWL value for the same amount of weight lost.

Can %EWL go above 100%? Yes. If your current weight is below the reference weight defined by your target BMI, %EWL exceeds 100%.

Is excess weight the same as body fat? No. Excess weight is the gap between current and reference weight on the scale. It does not measure fat mass directly and does not separate fat from muscle.